'Big Bang Theory' Season 9 Finale to End With Romantic Cliffhanger

Courtesy of Warner Bros. Entertainment

Showrunner Steve Molaro talks with THR about what to expect from this week's season-ender.

Will Penny (Kaley Cuoco) and Leonard (Johnny Galecki) finally have their formal wedding ceremony? That's the biggest burning question heading into Thursday's season nine finale of CBS' The Big Bang Theory— and, to hear showrunner Steve Molaro tell it, viewers may have to wait a bit longer to see the couple renew their vows.

Season nine opened with Leonard and Penny, picking up after season eight's cliffhanger, heading to Las Vegas to elope. While sweet, it seemed to have hurt Leonard's seemingly emotionless mother Beverly (Emmy winner Christine Baranski), and now Penny is tasked with staging a formal ceremony for all the couple's friends and family.

"Their wedding at beginning of the season, when you got into the vows, it got sweet and lovely very quickly but it didn't quite carry the weight of an actual ceremony with family and friends," Molaro tells The Hollywood Reporter. "That's at least Penny's goal: to try and make it up to her mother-in-law a little bit. But that means we have new characters coming to town and meeting for the first time. The way they get along may be enough story for before we actually get to the ceremony."

Enter comedy legend Judd Hirsch as Leonard's father, Dr. Alfred Hofstadter, who arrives in town for the re-nuptials and comes face-to-face with ex-wife Beverly, as well as Sheldon's mother, Mary (Laurie Metcalf), setting the stage for multiple new dynamics to be explored in the geektastic family comedy.

"It's great to see the dynamics between him and Leonard, which is all new," says Molaro. "There is a pretty acerbic and unpleasant relationship with him and his ex-wife Beverly, Leonard. As far as what is surprising about that, there might be a bit of an unexpected attraction springing up between Leonard's father and Sheldon's mother."

That dynamic, as would be expected, will make Leonard and Sheldon "pretty uncomfortable."

"We leave [the season] in typical Big Bang fashion — on bit of a cliffhanger with Leonard, Penny and Sheldon in the living room making sense of everything that's going on," Molaro says.

While there's a very clear wedding vibe in the air — look for a fancy family dinner that quickly turns awkward — could the series feature a surprise wedding for Sheldon (Jim Parsons) and Amy (Mayim Bialik)?

"I do not see any Sheldon and Amy surprise wedding in the near future," Molaro notes.

The Big Bang Theory season finale airs Thursday at 8 p.m. ET/PT on CBS. Stay tuned to THR's The Live Feed after the episode for more from Molaro.